wireless sensor system design

Wireless Sensor System DesignA Joint Course of the University of South Florida and Tennessee Technological UniversitySpring 2002

Lecture 7 - Wireless Communication Systems

USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMSTennessee TechUNIVERSITY

Weekly Lecture TopicsCourse IntroductionAnalog and Digital Modulation Methods (1/11)Fundamentals of Antennas and Propagation (1/18)Signal Processing Techniques (1/25)Microwave Systems: Communications Hardware, Noise, Linearity (2/1)System Test, Evaluation and Documentation / Effective Presentation Styles (2/8)Preliminary Design Review (student presentations*) (2/15)Microwave Sensor Technology (2/22) @ TTUModern Wireless Communication Systems (3/1)TBD (3/8)Critical Design Review (student presentations*) (3/22)Microelectromechanical Systems (MEMS) Sensors (4/5)Wireless Sensor System Research (Paul Flikkema from NAU) from USF (4/12)Review / Course Wrap-up (4/19)* On-site internal reviews/preparation will precede inter-university presentations.


OutlineWhy wireless communication systems?

Four examples of wireless telecommunications systems

Design criteria as related to class project


Wireless Communication Systems: WHY?Transmission mediaWired - wire/fiberWireless - airQuick installation of infrastructure e.g., straight to mobile in developing countriesUser mobilityShared accessTDMA FDMA or combinations of CDMA


Example 1: Satellite BroadcastingHUBShaped pattern22,400 miles


Example 1: Market for DirecTVTerrestrial Broadcast TVAn analog system of limited rangeEach channel occupies 6 MHzVHF (CH 2-13): 54-216 MHzUHF (CH 14-83): 470-890 MHzRegular Cable: same technology, just over wireNeed for an alternative?Cable not available everywhereCable had a monopolyAnalog system had a limited number of channel (82)


Example 1: TechnologyHigh-power direct broadcast satellite operating at Ku-band (14/12 GHz)All signals uplinked from single locationService (downlink) to any CONUS locationAnalog audio and video signals areDigitizedCompressed (MPEG-2, 8:1)EncodedMultiplexedInexpensive receivers


Example 1: Receiver TechnologyKu-band enables small receiving dish directivity ~1/Digital signal providesCD quality soundBetter pictureAdditional servicesMore channels: 500!


Example 1: SummaryPromise of high-quality, nation-wide service obtainedAdvantagesEasy to add new customers (database change)DisadvantagesLarge customer and venture investment up-frontNo standard among providersCompression can break downCable is catching up (Tom Switched!)Limited bandwidth, HDTV? Rainfade (FL - high gain slope and rain rates)


Example 1: Gain Slope & PointingHUBOKHUBNOTOK


Example 2: Cell phonesSpatial Isolation w/ channel groupsTime (TDMA)Freq (FDMA)Code (CDMA)Cell sizeCapacityPowersize 0 : wiredReuse: e.g., N=7 makes a clusterN - better isolationN - better reusemore clusters more reuse more capacity135642123473


Example 2: Changing CellsHandoffUses different set of channelschannel groups can be reused when cells are far apartreusing channel increases system capacity135642123473


Nice Geometry is not Reality!Source: University of Kansas' Information & Telecommunications Technology Center and Kansas Applied Remote Sensing Program


Example 3: WLAN: BluetoothCellular idea implemented in extremely small scale10 cm - 100 m (10 m nominal)2.4 GHz bandUp to 79 channels (@ 220 kHz) separated at 1 MHz intervalsLow power (RF and DC)FHSSThanks Asa


Example 3: Bluetooth ApplicationsInternet BridgeLaptopCell PhoneLANPeripheral InterfacePCPDAPrinterKeyboardMouseAware devices!


Example 4: Wireless Sensor SystemsWireless Sensing:Non-invasive, remote sensingWireless Link:Ease of installation - Low impactWide coverage regionUnique characteristic: Low bandwidth requirements

In this class weve discussed both wireless sensing and communications


Example 4: Wireless SensingActiveRadar and Lidar

Speed and positionPROXIMITYPassiveRadiometry and IR Imaging

CompositionThermal profile: measure emissivity for different wavelengths


Example 4: Wireless Link


Example 4 - Bottom LineWireless sensorsIn situ measurementNon-invasiveEase of placementMobilityUbiquitous


So what is next: Hype or Buzz?Three years ago:Satellite based global cellular systems

Two years ago:Satellite based broadband systems

Last few years:3G


So what is next the RealitySatellite based global cellular systemsIridium and Globalstar (bankrupt), ICO (DNS)

Satellite based broadband systemsTeledesic (designed and redesigned: 800 to 30 satellites), Spaceway, etc. still not launched

3G: Promise of mobile internet and telematicsIs there the bandwidth? Is there a standard?


So what is next the RealitySatellite based global cellular systemsIridium and Globalstar (bankrupt), ICO (DNS)

Satellite based broadband systemsTeledesic (designed and redesigned: 800 to 30 satellites), Spaceway, etc. still not launched

3G: Promise of mobile internet and telematicsIs there the bandwidth? Is there a standard?Is there a demand?


So what is happening?WLAN802.11b (11 Mbps) and Bluetooth (720 kbps)

Satellite based systemsXM and Sirius digital radioOnStar telematics

In building wirelessYour mobile phone becomes part of the company exchange inbuildingMaintains regular mobile functions off-campus

SEEMS THE FIELD IS MARKET DRIVEN!


Comm Systems: Pertinent Design CriteriaThe bottom line: What signal quality do you need?

Quantified by Signal-to-Noise Ratio (SNR)

Optimize signal power (S) and bandwidth (B) given noise constraintsDrives the design of:AntennasAmplifiersRange

Data RatesFiltersProcessingEverything


Wireless Communications SummaryWireless advantages:Mobility and potentially reduced infrastructure costsWireless disadvantages:Limited bandwidth and more expensive user devicesControl Power and Bandwidth to achieve desiredSNR ratio (signal quality)RangeData rates


Design Criteria as Related to ProjectRangefrequency of operation, amplifier gains, antennas, etc.BeamwidthDirectivity vs. beamwidthBandwidthBaseband limited by soundcard < 20 kHzRF limited by FCC ISM band constraintsFilters, sampling rates, etc.Signal levels (RF, baseband and DC)


Signal LevelsSensor to Baseband TXBaseband TX to IF TXIF TX to RF TXWireless Link: RF TX to RF RXRF TX to IF TXIF TX to Baseband RX



Bottom Line: Sensor to PCCan link be transparent to system?



Bottom Line: Sensor to PCCan link be transparent to system?DC requirements


ReferencesGagliardi, Introduction to Communications Engineering, 2nd Edition.Rappaport, Wireless Communication SystemsUlaby, et. al., Microwave Remote SensingTelecommunication systemswww.directv.comwww.bluetooth.com, www.bluetooth.orgSensor systemswww.atstrack.com


Two Month Course ScheduleFebruaryWeek 4 (28-1)First progress reportWeek 5 (4-8)Review peer reportsWeek 6 (11-15)Preliminary Design ReviewWeek 7 (18-22)Weller at TTU

MarchWeek 8 (25-1)Second progress reportWeek 9 (4-8) Review peer reportsSpring Break (11-15)Week 10 (18-22)Critical Design ReviewWeek 11 (25-29)No TTU class (F)1. All inputs are due on Friday of the specified week - no exceptions2. Reviews of peer reports must be completed before the lecture on Friday


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